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Title: Scanning tunneling microscopy study of morphology and electronic properties in (K{sub 0.7}Na{sub 0.3})Fe{sub 2−y}Se{sub 2} single crystal

We investigated the microstructure of the iron selenide superconductor (K{sub 0.7}Na{sub 0.3})Fe{sub 2−y}Se{sub 2} with a T{sub c} = 32 K and a near 100% Meissner screening volume fraction. Topography and electron transport properties were studied using electron microscopy and ultra-high vacuum scanning tunneling microscopy (STM) techniques. Room temperature STM measurements reliably identify spatial variations of the local electronic properties of this material. The studied crystals consist of continuous regions with significantly different shapes of current-voltage curves reflecting different electronic transport properties of these regions. Fitting of the local current-voltage curves with the Simmons model for metal-dielectric-metal structure confirmed a phase separation in the sample to a metal and semiconducting phases. The observed regions have dimensions in the range of several tenths of a micrometer and indicate a phase separation in the sample.
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ; ; ;  [5] ;  [6] ;  [3] ;  [2] ;  [2]
  1. Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 1(2), Leninskie Gory, GSP-1, Moscow 119991 (Russian Federation)
  2. (Russian Federation)
  3. Low Temperature Physics and Superconductivity Department, Physics Faculty, Lomonosov Moscow State University, 119991 Moscow (Russian Federation)
  4. Institute for Materials Research, Tohoku University, 980-8577 Sendai (Japan)
  5. Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow (Russian Federation)
  6. National Institute for Material Science, Tsukuba 305-0047 (Japan)
Publication Date:
OSTI Identifier:
22308539
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 4; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DIELECTRIC MATERIALS; ELECTRIC CONDUCTIVITY; ELECTRICAL PROPERTIES; ELECTRON MICROSCOPY; IRON COMPOUNDS; MICROSTRUCTURE; MONOCRYSTALS; POTASSIUM COMPOUNDS; SCANNING TUNNELING MICROSCOPY; SELENIUM COMPOUNDS; SODIUM COMPOUNDS; SUPERCONDUCTORS; TEMPERATURE RANGE 0013-0065 K; TEMPERATURE RANGE 0273-0400 K; TRANSITION TEMPERATURE